Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
US students often rank poorly on standardized tests that estimate and compare educational achievements. We investigate whether this might reflect not only differences in ability but also differences in effort on the test. We experimentally offer students incentives to put forth effort in two US high schools and four Shanghai high schools. US students improve performance substantially in response to incentives, while Shanghai students—who are top performers on assessments—do not. These results raise the possibility that ranking countries based on low-stakes assessments may not reflect only differences in ability, but also motivation to perform well on the test.